1. Field of the Invention
This invention relates to the field of reading of light-sensitive nodes which are mainly provided with a photodiode.
2. Description of the Prior Art
Reading of light-sensitive nodes at which provision is made for a photodiode is usually carried out in the prior art by means of switching elements which control the read operation.
In order to simplify the manufacturing processes, attention can be directed to structures of light-sensitive elements in which no switching element is provided. In this case, a signal in the form of pulses is employed for the read operation in order to control the discharge of a capacitor associated with the photodiode. This type of structure makes it possible to form matrices having large dimensions now that the techniques of thin-film deposition of amorphous silicon, for example, have been completely mastered.
When reading analog signals of small amplitude by means of matrices of this type, however, the charge stored within the light-sensitive elements is not completely read if the value of the conduction current is too low to permit removal of all the charges.